Early in the morning we had been kitted up in wetsuits - mine with a hole cunningly concealed under the right armpit - crash helmets and headlamps before being driven up the Grey Valley to the old gold mining area of Nelson Creek.
Before we started, Paul Schramm, the boss of Wild West Adventures, wanted to show me one of his ideas for making this particular adventure even wilder: a massive flying fox running from a clifftop through the trees and over the water to the launch point for the tubing trip. It looked fantastic but, sadly, while the flying fox had been tested with weights it hadn't been approved for use by humans, so we had to walk through the bush and up the creek before hopping aboard our vessels.
Piloting a tube down a winding, shingly South Island river takes a special set of skills involving using your hands to steer, keeping your feet poised to fend off the mossy stone cliffs and being ever-ready to lift your backside out of danger should you happen to sail over the top of a large boulder.
I can't say I proved skilled at this - several times I ended up bumping through the shallows - but unlike the big Aussie guy I didn't fall off my tube after surging through one of the rapids, and unlike the the young miner from Chile, I didn't get stuck on top of a rock and have to get up and walk.
Most of the time it was quite tranquil, allowing me to lie back and muse on how different it all must have been here back in 1870, when dozens of miners were busy digging and sluicing in this very area in pursuit of gold.
But this daydreaming was interrupted when we came to the end of our river ride and moved on to the blackwater part of the outing: tubing down an 840m long tunnel the miners dug around 1910 to get water for sluicing.
Getting into the tunnel is already pretty stimulating because it involves zooming at high speed on a natural rock slide down the bank. But Paul has plans to make it even more exciting by offering a sort of controlled bungee jump down a 22m-high ventilation shaft into the tunnel.
That particular scheme is still in the planning stages but Paul was able to show me the top of the shaft, looking like a narrow gateway into a black nothingness, and pictures of the gadget that will make the jump possible, a Powerfan, which apparently lets you drop at near free-fall speed, before slowing up in time to land gently.
It sounded like fun, but I'm not sure it would compare in shock value with the slide experience, which saw me hurtle below the surface of the ice cold water flowing from under the earth, literally taking my breath away.
Once we were breathing normally again we squelched our way a couple of hundred metres up the tunnel to the bottom of the ventilation shaft, took to our tyres and drifted gently back to the entrance, taking the opportunity to lie back and watch the glow worms twinkling on the roof.
After that there was one final piece of madness. Those who wished had the chance to step off a cliff, holding their tyres to their butts, and try to land on them on the river below. The big Aussie guy suddenly had back problems. The Asians were definitely not interested. So that was just me and the Chilean miner.
I stepped off first, soared elegantly down and landed right on the tube, which sprang back from the water hard enough to throw me off. I don't know how the Chilean did. I was too busy getting the water out of my eyes, nose and mouth to be able to see.
CHECKLIST
Getting there: Air New Zealand flies to Westport and Hokitika. Thrifty Car Rentals can deliver cars to both airports and several other points down the coast.
Where to stay: Breakers boutique accommodation sits on a clifftop above the Tasman about 14km north of Greymouth. Owners Jan and Stephen are wonderful guides to the area's secret places and also make a mean pizza.
What to do: Wild West Adventures offers a variety of activities, including Taniwha Cave Tubing, from its base in Greymouth.
Further information: See west-coast.co.nz.
Jim Eagles went to Greymouth with help from Tourism West Coast and Air New Zealand
